如何使用Julien Schmidt的路由器避免Go中的全局变量？

Question

I am developing a RESTful API with Go but owing to app configuration, authentication etc I have quite a few global variables.

I am using Julien Schmidt's httprouter because of popular recommendation and am looking for a feasible way to avoid global variables.

Here is some of the code.

I am using a middleware for authenticating a user using gorrila/securecookie.

func AuthMiddleware(handler httprouter.Handle, isLoggedIn bool) httprouter.Handle {
    return func(w http.ResponseWriter, r *http.Request, ps httprouter.Params) {if isLoggedIn {
            currUser, err := GetCurrentUser(r)

            if currUser.Username != "" {
                handler(w, r, ps)
                return
            }

            responseWriter(w, false, "User not logged in", nil)
            return
        }
        handler(w, r, ps)
    }
}

After this, I want to be able to use the currUser object inside the handler that the request is forwarded to such as this one instead of calling GetCurrentUser once again

func foobar(w http.ResponseWriter, _ *http.Request, _ httprouter.Params) {
    var currQuestion CurrQuestions

    err = Db.db.Raw("SELECT * FROM users WHERE U.user_id = ?", currUser.UserID).Find(&currQuestion).Error
    if err != nil {
        responseWriter(w, false, "Internal Server Error", "")
        return
    }
    responseWriter(w, true, "", GameData{})
}

Answer 1

You can use the context package. Values stored in context are only accessible in the current controller. In your middleware (at the end) do the following:

ctx := context.WithValue(r.Context(), "User", user)
r = r.WithContext(ctx)
handler(w, r, ps)

Now you can fetch this value in you handler:

user, ok := r.Context().Value("User").(<type of your user struct>)

The string "User" is the key that is used to save the value. You can change it any way you like, but a const is a good idea.

if ok is true, the user has been fetched and is the correct type. If ok is false, the user was not set or it has the wrong type.